1. Field of the Invention
This invention relates to an apparatus and method of reading indicia by analysis of noisy signals. In particular the invention relates to the reading of indicia having spaced apart regions of two different light reflectivities, such as bar code symbols.
2. Description of the Related Art
Various optical readers and optical scanning systems have been developed for reading indicia such as bar code symbols appearing on an article. The symbol itself is a coded pattern of indicia comprised of, for example, a series of bars of various widths spaced apart from one another so as to bound spaces of various widths, the bars and spaces having different light reflecting characteristics. The readers electro-optically transform the indicia into electrical signals, which are decoded into alphanumeric characters that are intended to be descriptive of the article or some characteristic thereof. Such characteristics are typically represented in digital form and utilized as an input to a data processing system for applications in point-of-sale processing, inventory control and the like.
Often the bar code symbol to be read is imperfectly printed, for example voids appear in the bars. Such defects in the printed symbols cause noise to appear in the electrical signals representing the symbols. Such problems arise, for example, where a badly printed indicia appears on a clean background. In such cases ink spread and voids may have been introduced during the printing process, for example when the indicia includes dot matrix printed symbols, as well as dirty or damaged symbols. Such ink spread and voids may lead to errors and inaccuracies in reading the indicia. In conventional readers for bar code symbols the bar code symbols are generally analyzed by examining the edges or transitions between bars and spaces, treating the bars and spaces as areas of differing light reflectivities. In some cases, however, such a technique is rendered less effective by imperfectly printed symbols which give rise to noise in the corresponding signal.
It is a general object to the present invention at least to alleviate some of the problems of the prior art.
It is a further object to provide a reader for reading printed indicia such as bar codes that provides improved reading of badly printed indicia.
It is yet a further object of the invention to provide a reader capable of reading at a high resolution.
It is a still further object of the invention to provide an improved method of reading indicia.
Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the followed detailed description, as well as by practice of the invention. While the invention is described below with reference to preferred embodiments, it should be understood that the invention is not limited thereto. Those of ordinary skill in the art will recognize additional applications, modifications and embodiments in other fields which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of significant utility.